Process of treating sulfid ores of lead.



ROBERT. DE LUGE, or OAKLAND, CALIFORNIA.

PROCESS OF TREATING SULFID ORES 0]? LEAD.

No Drawing.

To all whom it may concern.-

Be it known that I, ROBERT DE Loon, a citizen of the United States, residing at Oakland, in the county of Alameda and State of California, have invented certain new and useful Improvements in Processes of Treating Sulfid Ores of Lead, of which the following is a specification.

This invention is a hydrometallurgical process for recovering lead from its sulfid ores. The process is applicable to the treatment of rich sulfid ores of lead; or of mixed sulfid ores of which lead is an important component; or of poor ores of the same, provided these are silicious in character and reasonably free from lime or iron in soluble form. The process is capable of yielding lead in commercially pure metallic state, without preliminary roasting of the ore or subsequent refining of the metal. The process moreover may be so operated as to yield sulfur in marketable form, and to serve for the extraction of silver and copper accompanying lead in its sulfid ores.

I prefer to carry out my process in the following mannerz- The pulverized ore is treated in a suitable vessel with hot concentrated solution of ferric chlorid. The solution is agitated and kept at a boiling temperature for a number of hours. Complete decomposition of the ore is accomplished; the sulfur is freed as a white powder or slime, the lead being converted into chlorid of lead of which a small percentage will pass into solution, the rest remaining with the sulfur as slime. The ferric chlorid gives up chlorin to the lead of the ore and is thereby reduced to ferrous chlorid. A solution containing fifteen parts by weight of ferric chlorid to one hundred parts of water gives satisfactory results. As lead sulfid is rather difiicult to decompose, the finer the ore is ground and the stronger the solution of ferric chlorid, the more rapidly will this first stage of the process be completed. Agitation is also an assistance in securing rapid action.

The first solution is filtered from the slime and sent hot to the anode compartment of an electrolytic diaphragm cell, being there subjected to the electric current which restores it to the ferric condition after which it is fit for re-use to decompose fresh portions of sulfid ores. No lead is deposited in the anode compartment as long as ferrous chlorid is present. The ferrous chlorid also Specification of Letters Patent.

Patented Jan. 1, 1918.

Application filed May 8, 1917. Serial No. 167,334.

acts to reduce the back electromotive force of the cell and protects the carbon or gra hte anodes from polarization effects and islntegration from active oxygen or chlorin.

A'second solution containing 12 per cent. approximately of ferrous chlorid is used to leach the slime and dissolve the lead chlorid. This solution at a temperature of 90 C. will be saturated with about three per cent. of lead chlorid. After leaching the slime, the solution is filtered and sent to the cathode compartment of an electrolytic diaphragm cell and electrolyzed to deposit the lead. After the major portion of the lead is deposited from the solution, the latter is returned to the slime tank for a new cycle of operations.

When electrolyzing the solutions, as described above, using carbon anodes, sheet 25 steel cathodes, porous silica diaphragms and a distance of 2%,; inches between electrodes,

a current of ten amperes to the square foot will flow at a potential of about 2.2 volts. Lead is deposited in loose-crystalline form, and no evolution of hydrogen occurs as long as lead chlorid remains in solution adjacent to the cathode. Hence it is advisable to arrange for circulation of electrolytesduring the electrolyzing process. The current efficiency is close to the theoretical (six pounds of metallic lead per 746 ampere hours) unless .an intermingling of ferric solution from the anode compartment occurs, in which case no lead is deposited as long as ferric compounds remain in solution adjacent the cathode.

After the lead is all leached out of the slime, the latter may be washed, dried and distilled to extract the sulfur.

A moderately high temperature, say 70 to C., is advantageous throughout the process, and to secure such temperatures economically all containing vessels and pipes are preferably covered with heat-insulating 100 material, and all vessels that require openings for access should have removable covers. The first solution is a slow but powerful corrosive agent and requires about the same materials for containing vessels and 5 pipes that nitric would need under said conditions of temperature. The second solution is nearly neutral and offers no unusual difliculty in handling.

As will be seen, the above process is cyclic and is carried on by two separate solutions, each having a different function and kept separated throughout the process. The first solution decomposes the ore, frees the sulfur and produces the chlorid of lead, being itself reduced from the ferric to the ferrous condition, and being then sent to the anode compartment of a diaphragm cell andelectrolyzed to oxidize it to the ferric state, after which it is sent back to the initial stage of the cycle to decompose fresh portions of sulfid ore. Although this solution contains small percentages of lead, no effort need be made to extract the same during the ordinary working of the process.

The second solution is merely a vehicle for dissolving, transporting and depositing, by electrolysis, the lead that is contained in the slime produced by the first solution in the first stage of the process. The reason the second solution is made to contain ferrous chlorid is to increase the electrolytic conductivity and so make possible large current densities. No increase of solubility of lead salts is secured thereby, as pure water would dissolve slightly more lead chlorid without the presence of other chlorids. Any other common electrolyte such as chlorid of sodium could be used in place of ferrous chlorid to produce the same result and increase the conductivity of the solution, but ferrous chlorid is chosen as being most convenient. This solution is kept free from ferric compounds as such will only waste current by being reduced at the cathode into the ferrous state.

Should the ore contain copper or silver, they will be found in the slime in the first stage of the process and will subsequently pass into solution with the lead and be deposited with the lead on the cathode during electrolysis, so that the lead would require a subsequent refining operation to free it from silver and copper. To avoid this difficulty, an additional cell or cells may be provided without diaphragms and with soluble anodes such as iron or lead. After leaching the slime, the second solution is circulated through these cells while an electric current is flowing, the silver and copper are deposited upon the cathode plates, and the solution is then sent to the diaphragm cells and treated for deposition of lead, as described above.

When antimony, bismuth, zinc and iron occur in the lead ore, they will accumulate in the first solution which may be treated for them Whenever their amounts become considerable.

Where reference is made to the anode and cathode compartments of an electrolytic cell having a porous diaphragm, it will be understood that for simplicity and economy of installation and operation, it is desirable that the first and second solutions should flow, respectively, through the anode and cathode compartments of the same cell, or series of cells. This it not, however, essential for carrying out the invention, it being necessary only that these solutions be subjected respectively to anodic and cathodic action.

I claim 1. A process of treating sulfid ores of lead, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue with an electrically conductive solution having a practicable solvent capacity for lead chlorid, and free from ferric compounds, and subjecting said solutions respectively as electrolytes to anodic and cathodic action.

2. A process of treating sulfid ores of lead, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue With an electrically conductive solution having a practicable solvent capacity for lead chlorid and free from ferric chlorid, and simultaneously electrolyzing said solutions in the anode and cathode compartments respectively of an electrolytic cell having a porous diaphragm.

3. A process of treating sulfid ores of lead, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue with a chlorid solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, and subjecting said solutions respectively as electrolytes to anodic and cathodic action.

4. A process of treating sulfid ores of lead, comprising decomposing the ore bv a solution containing ferric chlorid, leaching the residue with a chlorid solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, and simultaneously electrolyzing said solutions in the anode and cathode compartments respectively of an electrolytic cell having a porous diaphragm.

5. A cyclical process of treating sulfid ores of lead, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue with an electrically conductive solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, subjecting said solutions respectively as electrolytes to anodic and cathodic action to effect their regeneration and to deposit lead, and re-using said solutions for the decomposition and leaching'of fresh batches of ore in a repetition of the cycle.

6. A cyclical process of treating sulfid ores of lead, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue with an electrically conductive solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, simultaneously electrolyzing said solutions in the anode and cathode compartments respectively of an electrolytic cell having a porous diaphragm, thereby regenerating said solutions and depositing lead, and

re-using said solutions for the decomposition and leaching of fresh batches of ore in a repetition of the cycle.

7. A process of treating sulfid ores of lead, containing silver or copper, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue With an electrically conductive solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, precipitating the less electropositive metals from said sec ond solution, and subjecting said solutions respectively as electrolytes to anodic and cathodic action to eflet' their regeneration and to deposit lead.

8. A process of treating sulfid ores of lead containing silver or copper, comprising decomposing the ore by a solution containing ferric chlorid, leaching the residue With an electrically conductive solution having a practicable solvent capacity for lead chlorid, and free from ferric chlorid, depositing the less electropositive metals from said second solution by electrolysis with a soluble anode, and subjecting said solutions respectively as electrolytes to anodic and cathodic action to effect their regeneration and to deposit lead.

In testimony whereof I aflix my signature in presence of two Witnesses.

ROBERT DE LUCE.

lVitnesses PEARL B. MILLER, MAX YV. STERN. 

